Roger Long wrote:
"Gary" wrote Hydrodynamic lift illustration

As you can see in the attachment, the boat is sailing to windward on
a
close reach or close hauled. Notice how the boat does not sail
perfectly
straight, but rather at a slight angle (yaw)(angular component).


That would be leeway, right?
Once again, the goal being to minimize leeway and heel to gain maximum
speed.

You have conveniently snipped your initial statement that was the
genesis of our discussion:

"Balance of sailboats is a huge myth. The whole CP, CLR, Lead business
was just a way for yacht designers to look scientific. The fact that
you can make huge area changes, such as the mizzen, without much helm
angle change shows how silly the whole idea is. There are schooners
with 10% negative lead and they sail fine."

I still call you on it!

You've had yours pulled ;-)

http://www.navy.gc.ca/oriole/crew/sh...mandteam_e.asp

Of course your designs might not respond to huge sail area changes.
They are not exactly leading edge technology, but I am a fan of classic
boats. (I own a Bill Garden sloop)

"Gary" wrote in

You have conveniently snipped your initial statement that was the
genesis of our discussion:

Oh, all right.

Moving the sail plan fore and aft will have an effect on the angle of
the rudder and the amount of helm force. However, very large changes
in the distribution of sail area have very modest effects. If the sail
plan looks normal, the boat will work just fine. Very small changes in
distribution that require the calculations that are so prominent in
yacht design books are only going to change the rudder angle by small
amounts and the helm force in ways you would have to make direct
comparisons between identical boats under controlled conditions to
detect.

Boats do turn out having excessive weather helm. When this happens, it
has more to do with the hull dynamics and rudder design than the sail
balance. It isn't because the designer set the lead at 10% instead of
12% or even 15%. The kind of things that can be done by tweaks like
raking the mast less are not going to turn a heavy helmed boat into a
well balanced one. They will help a little but the psychological
effect will far outweigh the actual change in helm force.

People will tell you that they have solved their weather helm by
adjusting mast rake but they have also really been paying attention to
the boat and their steering during the tweaking process. They are
tweaking other things besides the fore and aft position of the rig,
like leech tightness. During the process, they get to know the boat
better and their helmsmanship improves.

In racing boat design, where you are trying to wring every bit of
performance out of the boat, you might care whether the rudder was at
a 1.5 degree instead of a 2 degree angle in a 16 knot wind with a
perfect set of sails. In that case, you might look at the lead of
similar boats. For cruising, and even racing among dissimilar boats,
you're just fooling yourself. The rudder angle is going vary within
several degrees depending on how hard the boat is being driven and
other factors. Mast rake adjustment will also create detectable
differences when you are obsessing about fine performance and looking
carefully but this isn't the same thing as the distinction between a
boat with heavy weather helm and a well balanced one.

All else being equal, the amount of lead just establishes the wind
speed at which helm angle will be absolutely optimum. The more lead,
the higher the wind velocity. Too much lead and you will have lee helm
in light air but this it pretty hard to achieve in most boats without
a bowsprit.

Balance in boats is real but the typical presentation of it in yacht
design books and articles and the C.P. / C.L.P. business is a complete
crock.

--

Roger Long

"Gary" wrote:

You've had yours pulled ;-)

So I have. I missed your the link when I wrote last night. (You can
tell that New Years isn't a big deal at our house.)

This turns out to be one of those newsgroup exchanges where two people
who actually do know what they are talking about hurl darts back and
forth reacting to simple statements and imprecise language. Clearly,
you were not trying to tell me that keels develop side force at zero
angle of attack, etc.

Aside from providing entertainment for the bystanders, these cyber arm
wrestling matches can be educational. I'm sure anything we say from
this point on we'll both find that we actually understand and agree on
when we dig deep enough into it.

Many of these discussions get kicked off by absolutes. I can't
remember if it was my statement or someone else's' but the proposition
that a freewheeling prop has more drag kicked off a long thread a
while ago. It's a true statement in that it will apply to the majority
of auxiliary sailing vessels and engine installations. In the
exceptions, the savings from freewheeling will be too small to be
worth the vibration and bearing wear. It is not a theoretically
accurate statement however because there are exceptions. If the
friction, pitch, and size relationships are right, freewheeling may
produce less drag at certain speeds. It's just not common.

The contribution of weather helm to performance is a similar issue.
The symmetrical keel requires an angle of attack to develop the
necessary lift. As you have pointed out, (and I have agreed while
sniping at you for thinking you were saying the opposite) the
resulting yaw increases resistance. The rudder can develop side force
lift without requiring a corresponding yaw angle of the hull as a
whole.

Small rudder angles can (that's "can"; not "will", "always", or
anything like that) increase speed made good to windward by developing
side force that does not carry the penalty of increased leeway. As the
angle increases however, the lift vector of the rudder is increasingly
aft and drag greater so the contribution quickly becomes negative. It's
a lot like my plane, the first 10 degrees of flaps increase lift with
very little change in speed. As I put them down further, they
transition into being primarily speed brakes.

My boat has a reputation for having weather helm. Driven hard in fresh
breezes, it carries a large rudder angle and a huge wash under the
transom. The angle is 15 degrees or more so there is certainly a lot
of drag but it is also nearly up to hull speed by this point so it is
not going to go a lot faster anyway. The boat remains very
controllable as I have noted and sailing it as I have posted before
makes the helm tolerable. Still, it would be nice to sail in those
conditions with just 2 or 3 degrees of rudder.

This situation does not exist on my boat because the lead is 15%
instead of 20%. No amount of sail area distribution without adding a
bowsprit would change the situation significantly. Moving the rudder
all the way aft to the transom would take a degree or two off the
angle because of the increased lever arm but that wouldn't turn it
into a boat that didn't have a reputation for weather helm. Moving the
leading edge of the keel way aft would have helped. The keel then
would have needed to be deeper to develop the necessary area. The boat
would be harder to haul out and in more danger if it dries out after
running aground (a real consideration for the kind of sailing in out
of the way places I plan to go). This kind of change might take
another couple degrees off the rudder angle.

The biggest change, as you have said and I have agreed in backhand,
would be achieved by an increase in stability. If I were designing a
new boat to be much like the E32, I would give it a bit more beam and
less keel volume (very thick as a heritage from the keel/centerboard
version).

All these changes are what I meant when I said (not too clearly) that
weather helm is more a function of the overall design than the
designer's fiddling with paper cut outs of the underbody.

Nice playing darts with you. Next time, we'll use a target.

--

Roger Long

Roger Long wrote:
"Gary" wrote:


You've had yours pulled ;-)


So I have. I missed your the link when I wrote last night. (You can
tell that New Years isn't a big deal at our house.)

This turns out to be one of those newsgroup exchanges where two people
who actually do know what they are talking about hurl darts back and
forth reacting to simple statements and imprecise language. Clearly,
you were not trying to tell me that keels develop side force at zero
angle of attack, etc.

Aside from providing entertainment for the bystanders, these cyber arm
wrestling matches can be educational. I'm sure anything we say from
this point on we'll both find that we actually understand and agree on
when we dig deep enough into it.

Many of these discussions get kicked off by absolutes. I can't
remember if it was my statement or someone else's' but the proposition
that a freewheeling prop has more drag kicked off a long thread a
while ago. It's a true statement in that it will apply to the majority
of auxiliary sailing vessels and engine installations. In the
exceptions, the savings from freewheeling will be too small to be
worth the vibration and bearing wear. It is not a theoretically
accurate statement however because there are exceptions. If the
friction, pitch, and size relationships are right, freewheeling may
produce less drag at certain speeds. It's just not common.

The contribution of weather helm to performance is a similar issue.
The symmetrical keel requires an angle of attack to develop the
necessary lift. As you have pointed out, (and I have agreed while
sniping at you for thinking you were saying the opposite) the
resulting yaw increases resistance. The rudder can develop side force
lift without requiring a corresponding yaw angle of the hull as a
whole.

Small rudder angles can (that's "can"; not "will", "always", or
anything like that) increase speed made good to windward by developing
side force that does not carry the penalty of increased leeway. As the
angle increases however, the lift vector of the rudder is increasingly
aft and drag greater so the contribution quickly becomes negative. It's
a lot like my plane, the first 10 degrees of flaps increase lift with
very little change in speed. As I put them down further, they
transition into being primarily speed brakes.

My boat has a reputation for having weather helm. Driven hard in fresh
breezes, it carries a large rudder angle and a huge wash under the
transom. The angle is 15 degrees or more so there is certainly a lot
of drag but it is also nearly up to hull speed by this point so it is
not going to go a lot faster anyway. The boat remains very
controllable as I have noted and sailing it as I have posted before
makes the helm tolerable. Still, it would be nice to sail in those
conditions with just 2 or 3 degrees of rudder.

This situation does not exist on my boat because the lead is 15%
instead of 20%. No amount of sail area distribution without adding a
bowsprit would change the situation significantly. Moving the rudder
all the way aft to the transom would take a degree or two off the
angle because of the increased lever arm but that wouldn't turn it
into a boat that didn't have a reputation for weather helm. Moving the
leading edge of the keel way aft would have helped. The keel then
would have needed to be deeper to develop the necessary area. The boat
would be harder to haul out and in more danger if it dries out after
running aground (a real consideration for the kind of sailing in out
of the way places I plan to go). This kind of change might take
another couple degrees off the rudder angle.

The biggest change, as you have said and I have agreed in backhand,
would be achieved by an increase in stability. If I were designing a
new boat to be much like the E32, I would give it a bit more beam and
less keel volume (very thick as a heritage from the keel/centerboard
version).

All these changes are what I meant when I said (not too clearly) that
weather helm is more a function of the overall design than the
designer's fiddling with paper cut outs of the underbody.

Nice playing darts with you. Next time, we'll use a target.

I was learning the entire time. I was particularly interested in jibing
centerboards. Very interesting.

Gaz

On Sun, 01 Jan 2006 13:14:55 GMT, "Roger Long"
wrote:

The biggest change, as you have said and I have agreed in backhand,
would be achieved by an increase in stability.

=======================

Racing boats do this all the time by loading up the rail with crew,
and it is very effective. There is a rule of thumb which states that
a pound of weight on the rail is worth two pounds in the keel.
Depends on the boat of course, but crew weight acts on stability
immediately, whereas ballast weight has to be heeled at some angle
first.

That said, flattening the mainsail by any means possible, and pulling
the draft further forward is also very effective at reducing weather
helm.

Wayne.B wrote:
On Sun, 01 Jan 2006 13:14:55 GMT, "Roger Long"
wrote:


The biggest change, as you have said and I have agreed in backhand,
would be achieved by an increase in stability.


=======================

Racing boats do this all the time by loading up the rail with crew,
and it is very effective. There is a rule of thumb which states that
a pound of weight on the rail is worth two pounds in the keel.
Depends on the boat of course, but crew weight acts on stability
immediately, whereas ballast weight has to be heeled at some angle
first.

That said, flattening the mainsail by any means possible, and pulling
the draft further forward is also very effective at reducing weather
helm.

Careful. The chap you are preaching to is the Chaplain. Google Roger
Long before you get to far into this. I should have.

Gaz

On Tue, 03 Jan 2006 05:03:00 GMT, Gary wrote:

Careful. The chap you are preaching to is the Chaplain. Google Roger
Long before you get to far into this. I should have.
===========================================

I'm aware that Roger is an experienced marine architect but that does
not necessarily make him a sailing expert. I have spent literally
thousands of hours racing keel boats (with some success), so I'm
fairly comfortable discussing what has worked for me. I think we all
agree that reducing heel angle will help to reduce weather helm but
there are various ways of doing that.

Wayne.B wrote:

I think we all
agree that reducing heel angle will help to reduce weather helm but
there are various ways of doing that.

I had a lesson once on how much immersed asymmetrical hull
form has to do with it; too much when heeled and there will
be a rounding up force that must be corrected by the rudder.
I took the helm of a cruising folkboat for the first time as
we were clearing the Firth of Forth on the east coast of
Scotland. As we cleared the shelter of the firth a strong NE
wind caused her to bury her rail but I was amazed that the
tiller remained light, responsive and only a tad off central
- a beautifully balanced yacht at any angle of heel.
BrianH.

If you do the silly yacht designer's thing of cutting out the hull
profile and balancing it on a pin you will find that the lead of the
Folkboat isn't much different that vessels with lots of weather helm.
What started this whole sub thread was my not to clearly stated
assertion that it is not fine tuning of the C.E. / C.L.P relationship
that determines helm balance but lots of other factors.

--

Roger Long



"BrianH" wrote in message
...
Wayne.B wrote:

I think we all
agree that reducing heel angle will help to reduce weather helm but
there are various ways of doing that.

I had a lesson once on how much immersed asymmetrical hull form has
to do with it; too much when heeled and there will be a rounding up
force that must be corrected by the rudder. I took the helm of a
cruising folkboat for the first time as we were clearing the Firth
of Forth on the east coast of Scotland. As we cleared the shelter of
the firth a strong NE wind caused her to bury her rail but I was
amazed that the tiller remained light, responsive and only a tad off
central - a beautifully balanced yacht at any angle of heel.
BrianH.

I may not be a sailing expert (although I have fooled the British
Government, most of the sail training organizations in the U.S., and
the U.S. Coast Guard into thinking so) but I was very intrigued by the
balance issue in my early years.

The centerboard and rudder comprise just about the whole lateral plane
on a dinghy. If you remove the centerboard from a dinghy with a
hinged board and put in a temporary dagger boat, you can make huge
adjustments in the location of the lateral plane. If you study the
effect on rudder angle under controlled conditions you can learn some
very interesting things.

The racing adjustments you are talking about certainly are real and do
work. The difference is one of perspective. When attempting to eke
out very small increments of performance these small reductions in
rudder angle and helm force are significant. You may even see
yourself picking up enough speed, maybe .03%, to close the angle on
the boat next to you. It's sort of like a lot of sail trim
adjustments. Pulling the Cunningham will speed up a racing boat under
some circumstances but it will not convert a "slow" cruising boat into
a "fast" one.

These small changes observed while racing are not the same thing
though as the differences between boats that are considered to have
weather helm over a broad range of conditions and ones that are
considered well balanced. You are also not changing the crude
geometric C.E. / C.L.P. relationships very much but other critical
aerodynamic aspects of the sail plan that are not considered in the
paper on a pin approach.

--

Roger Long



"Wayne.B" wrote in message
...
On Tue, 03 Jan 2006 05:03:00 GMT, Gary
wrote:

Careful. The chap you are preaching to is the Chaplain. Google
Roger
Long before you get to far into this. I should have.
===========================================

I'm aware that Roger is an experienced marine architect but that
does
not necessarily make him a sailing expert. I have spent literally
thousands of hours racing keel boats (with some success), so I'm
fairly comfortable discussing what has worked for me. I think we
all
agree that reducing heel angle will help to reduce weather helm but
there are various ways of doing that.